4. Conclusion
Caffeine was extracted from roasted coffee, purified, and then bottled as RM. The purity % of this RM was certified by reversed-phase liquid chromatography/DAD and by UV/Vis spectrophotometry as two independent analytical techniques. The results obtained by the two methods were in very good agreement, and were combined to drive the certified value and its associated uncertainty. The certified caffeine purity was found to be 99.86% and the associated uncertainty to be ±0.65%. This high-purity caffeine CRM would be a very useful calibrant for analytical laboratories performing food and drug analysis.